1. Field of the Invention
The present invention relates to a signal generator, and more particularly to a signal generator for generating a signal at a required frequency using a harmonic signal having a frequency range in the ultra wide band (UWB).
2. Description of the Related Art
In a wireless communication system, a radio frequency (RF) signal received in a receiver is converted into an intermediate frequency (IF) signal by means of a mixer 10 as shown in FIG. 1. The mixer 10 mixes a signal delivered from a voltage controlled oscillator (VCO) 12 with the RF signal and converts the frequency of the mixed signal into the frequency of the IF signal.
As described above, the VCO included in the receiver is mainly used for channel selection. In order to be used for band selection, the VCO must have a wider frequency control range.
However, the conventional VCO shown in FIG. 2 cannot control a wide frequency range using only a varactor because a great number of parasitic capacitors exist in the VCO.
As shown in FIG. 3, a non-linear element generates harmonics with respect to a fundamental frequency f, and these harmonics are generated in a wide frequency band. Since these harmonics have very little power, the harmonics are unsuitable for oscillator signals.